The Third Generation Partnership Project Two (3GPP2) standard provides a compatibility standard for cellular mobile telecommunications systems. The 3GPP2 standard ensures that a mobile station (MS), or access terminal (AT), (hereinafter collectively referred to as an MS) operating in a cdma2000 (Code Division Multiple Access 2000) communication system (such as a 1X system or a HRPD system) can obtain communication services when operating in a system manufactured according to the standards. To ensure compatibility, radio system parameters and data transfer procedures are specified by the standards, including protocols governing digital control messages and bearer traffic that are exchanged over an air interface.
The 3GPP2 standards provide, in the X.P0022, A.S0019, C.S0054, C.S0005, and S.R0083 specifications, for delivery of a Broadcast-Multicast Service (BCMCS) by a cdma2000 communication system to MSs serviced by the system and subscribed to the Service. For example, a BCMCS may deliver one or more broadcast-multicast flows comprising audio, video, and/or data associated with a multimedia program such as a Cable News Network (CNN) newscast or an Home Box Office (HBO) movie or show.
In order to permit an MS subscribed to a broadcast-multicast flow associated with a BCMCS to receive and store and/or render the content of the flow, a BCMCS Controller conveys to the MS a flow identifier (BCMCS_FLOW_ID) associated with the flow, that is, with the particular program, such as CNN or HBO, subscribed to by the MS, a Broadcast Access Key (BAK) used to encrypt/decrypt the audio, video, and/or data associated with the flow, a BAK identifier (BAK_ID) that identifies the associated BAK, and an expiration time (BAK_Expire) at which the associated BAK expires (at which time a new BAK is employed). The BAK serves to protect the content of the flow from viewing by non-subscribers to the flow. The BCMCS Controller may further convey to the subscribed MS an identifier of an algorithm, such as MPEG4, used to compress data associated with the flow, and miscellaneous program-related information, such as a program date and a program start time or stop time. When a BCMCS Content Server associated with the BCMCS Controller receives BCMCS data associated with the flow, the BCMCS Controller instructs the BCMCS Content Server to encrypt the data using the BAK. The BCMCS Content Server then broadcasts the encrypted data via a Base Station (BS) or an Access Network (AN) servicing the MS. Each subscribed MS may then decrypt the broadcast audio, video, and/or data using the provided subscription key and store, and/or render to the user of the MS, the decrypted audio, video, and/or data.
In a communication system that provides a BCMCS, it is desirable to permit MSs serviced by the system to preview content of the broadcast-multicast flows associated with the BCMCS in order to entice the MSs, that is, users of the MSs, to subscribe to the flows. In order to permit an MS to preview content of a broadcast-multicast flow, the BAK used to encrypt the flow must be provided to the MS. However, providing the BAK to the MS amounts to giving away a free subscription to the broadcast-multicast flow until the BAK expires. In order to minimize the impact of the give away, the life of the BAK may be shortened, but the shorter the life of the BAK, the more complex the key management and the more system overhead is consumed in repeatedly conveying keys to MSs subscribed to the flow. Alternatively, previews may be broadcast unencrypted, but this may allow all MSs active in the communication system to view the content of the broadcast-multicast flow, including under-age users with respect to flows with adult content. Furthermore, a broadcast of an unencrypted preview may not allow a system operator to restrict a preview, such as a preview of a pay-per-view HBO broadcast, to a limited subscriber audience, such as only subscribers to HBO programming.
Therefore, a need exists for a method and apparatus for controlling a delivery of previews of broadcast-multicast flows in a packet data communication system.